The medical community needs an instrument to continuously and accurately monitor temperature at multiple locations in and around a tumor during hyperthermia therapy. Current temperature monitoring devices cannot satisfactorily meet this need. Optical Technologies, Inc. (OPTECH) has developed a unique fiber-optic sensor that can monitor temperature continuously and accurately at multiple locations by measuring temperature at more than one location on a single optical fiber, a significant technological innovation. Phase II will produce a commercial version of this sensor by developing production techniques that ensure ready manufacturability, and incorporating the sensor into a thermometer array. The sensor will have the following features: measurement of temperature at multiple locations in a single probe, small probe diameter (as small as 0.35 mm), accuracy (plus-minus 0.1 degree C), resolution (0.01 degree C), dielectric sensors, useable in microwave environments, thermal response of 1 degree C/sec, and reliability and safety (nonthrombogenic). The result will be a commercial quality fiber-optic temperature array that fills immediate need in hyperthermia therapy of cancerous tumors.